[Qemu-devel] [RFC PATCH 1/2] qdev: Add a hook for a bus to device if it can add devices

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

This allows a bus class to tell whether a given bus has room for
any new device. max_dev isn't sufficient as the rules can depend
on some arguments or can differ between instances of a bus. This
will be used by PCI in a subsequent patches

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 include/hw/qdev-core.h |  1 +
 qdev-monitor.c         | 13 ++++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 038b54d..025df40 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -189,6 +189,7 @@ struct BusClass {
      */
     char *(*get_fw_dev_path)(DeviceState *dev);
     void (*reset)(BusState *bus);
+    bool (*can_add_device)(BusState *bus, QemuOpts *opts);
     BusRealize realize;
     BusUnrealize unrealize;
 
diff --git a/qdev-monitor.c b/qdev-monitor.c
index f9e2d62..1ecb87e 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -382,7 +382,7 @@ static inline bool qbus_is_full(BusState *bus)
  * Return the bus if found, else %NULL.
  */
 static BusState *qbus_find_recursive(BusState *bus, const char *name,
-                                     const char *bus_typename)
+                                     const char *bus_typename, QemuOpts *opts)
 {
     BusChild *kid;
     BusState *pick, *child, *ret;
@@ -396,7 +396,10 @@ static BusState *qbus_find_recursive(BusState *bus, const char *name,
     }
 
     if (match && !qbus_is_full(bus)) {
-        return bus;             /* root matches and isn't full */
+        BusClass *bc = BUS_GET_CLASS(bus);
+        if (!bc->can_add_device || bc->can_add_device(bus, opts)) {
+            return bus;             /* root matches and isn't full */
+	}
     }
 
     pick = match ? bus : NULL;
@@ -404,7 +407,7 @@ static BusState *qbus_find_recursive(BusState *bus, const char *name,
     QTAILQ_FOREACH(kid, &bus->children, sibling) {
         DeviceState *dev = kid->child;
         QLIST_FOREACH(child, &dev->child_bus, sibling) {
-            ret = qbus_find_recursive(child, name, bus_typename);
+		ret = qbus_find_recursive(child, name, bus_typename, opts);
             if (ret && !qbus_is_full(ret)) {
                 return ret;     /* a descendant matches and isn't full */
             }
@@ -434,7 +437,7 @@ static BusState *qbus_find(const char *path, Error **errp)
             assert(!path[0]);
             elem[0] = len = 0;
         }
-        bus = qbus_find_recursive(sysbus_get_default(), elem, NULL);
+        bus = qbus_find_recursive(sysbus_get_default(), elem, NULL, NULL);
         if (!bus) {
             error_setg(errp, "Bus '%s' not found", elem);
             return NULL;
@@ -552,7 +555,7 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
             return NULL;
         }
     } else if (dc->bus_type != NULL) {
-        bus = qbus_find_recursive(sysbus_get_default(), NULL, dc->bus_type);
+	    bus = qbus_find_recursive(sysbus_get_default(), NULL, dc->bus_type, opts);
         if (!bus || qbus_is_full(bus)) {
             error_setg(errp, "No '%s' bus found for device '%s'",
                        dc->bus_type, driver);